Enhancing onion growth and yield quality via soil amendments and foliar nutrition under deficit irrigation

EVELOPING a modern approach to sustain strategic crop productivity under conditions of water scarcity is a matter that occupies the thoughts of all researchers in the field of agricultural scientific research. So, a research trial was performed during the growing season of 2022/ 2023 for improving the onion growth performance and its quantitative and qualitative yield under deficit irrigation via some soil amendments and some beneficial element spraying. Three irrigation regimes [ I 1 : Four irrigations, I 2 : Three irrigations and I 3 : Two irrigations were evaluated as main plots. The soil amendments [ T 1 : Without soil amendments), T 2 : Biochar, T 3 : Zeolite, T 4 : Compost (plant residues), at rate of 10 Mg ha -1 for each soil amendment] were evaluated as sub main plots. Also, the foliar application of nutrient elements [ F 1 : Without foliar application, F 2 : Boron, F 3 : Copper, F 4 : Selenium, at rate of 10 mg L -1 for each element ) was assessed as sub-main plots. Parameters expressing the growth performance ( e.g., foliage dry weight, chlorophyll, proline and catalase enzyme) at the period of 75 days from transplanting were determined. Also, traits expressing quantitative yield ( e.g., total and marketable bulb yield) and qualitative yield ( e.g., carbohydrate, protein, vitamin C, total dissolved solids and pyruvic acid) were estimated. The findings indicate that the traditional irrigation approach (I 1 ) caused the best performance in terms of both quantitative and qualitative yield. Following this, the water deficit treatments ( I 2 and I 3 ) resulted in lower performance, as the I 3 treatment led to the lowest performance. When considering soil amendments, compost proved to be the most effective, followed by zeolite, then biochar, while, the control treatment ( without soil amendments) was the least effective. Regarding the beneficial elements, the order of effectiveness from most to least was Se > Cu > B > F 1 (control). Generally, the most favorable outcomes were observed when combining compost ( T 4 ) with selenium foliar application ( F 4 ), within the framework of the traditional irrigation treatment ( I 1 ). Notably, the growth performance, as well as the quantitative and qualitative yield, were better when employing the combined approach of compost (T 4 ) and selenium foliar application (F 4 ) under the water deficit treatment (I 2 ) compared to plants grown traditionally without any of the studied substances (I 1 x T 1 x F 1 ). In conclusion, this research underscores the potential of soil amendments, and nutrient application strategies to enhance onion growth and yield under water scarcity. By continuously refining these approaches and embracing a holistic perspective, the agricultural community can move closer to ensuring food security and sustainability in challenging environmental conditions.